package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.Serializable;

import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.TokenStream;

/**
 * A Payload is metadata that can be stored together with each occurrence of a
 * term. This metadata is stored inline in the posting list of the specific
 * term.
 * <p>
 * To store payloads in the index a {@link TokenStream} has to be used that
 * produces {@link Token}s containing payload data.
 * <p>
 * Use {@link TermPositions#getPayloadLength()} and
 * {@link TermPositions#getPayload(byte[], int)} to retrieve the payloads from
 * the index.<br>
 * 
 */
public class Payload implements Serializable, Cloneable {
	/** the byte array containing the payload data */
	protected byte[] data;

	/** the offset within the byte array */
	protected int offset;

	/** the length of the payload data */
	protected int length;

	/** Creates an empty payload and does not allocate a byte array. */
	public Payload() {
		// nothing to do
	}

	/**
	 * Creates a new payload with the the given array as data. A reference to
	 * the passed-in array is held, i. e. no copy is made.
	 * 
	 * @param data
	 *            the data of this payload
	 */
	public Payload(byte[] data) {
		this(data, 0, data.length);
	}

	/**
	 * Creates a new payload with the the given array as data. A reference to
	 * the passed-in array is held, i. e. no copy is made.
	 * 
	 * @param data
	 *            the data of this payload
	 * @param offset
	 *            the offset in the data byte array
	 * @param length
	 *            the length of the data
	 */
	public Payload(byte[] data, int offset, int length) {
		if (offset < 0 || offset + length > data.length) {
			throw new IllegalArgumentException();
		}
		this.data = data;
		this.offset = offset;
		this.length = length;
	}

	/**
	 * Sets this payloads data. A reference to the passed-in array is held, i.
	 * e. no copy is made.
	 */
	public void setData(byte[] data) {
		setData(data, 0, data.length);
	}

	/**
	 * Sets this payloads data. A reference to the passed-in array is held, i.
	 * e. no copy is made.
	 */
	public void setData(byte[] data, int offset, int length) {
		this.data = data;
		this.offset = offset;
		this.length = length;
	}

	/**
	 * Returns a reference to the underlying byte array that holds this payloads
	 * data.
	 */
	public byte[] getData() {
		return this.data;
	}

	/**
	 * Returns the offset in the underlying byte array
	 */
	public int getOffset() {
		return this.offset;
	}

	/**
	 * Returns the length of the payload data.
	 */
	public int length() {
		return this.length;
	}

	/**
	 * Returns the byte at the given index.
	 */
	public byte byteAt(int index) {
		if (0 <= index && index < this.length) {
			return this.data[this.offset + index];
		}
		throw new ArrayIndexOutOfBoundsException(index);
	}

	/**
	 * Allocates a new byte array, copies the payload data into it and returns
	 * it.
	 */
	public byte[] toByteArray() {
		byte[] retArray = new byte[this.length];
		System.arraycopy(this.data, this.offset, retArray, 0, this.length);
		return retArray;
	}

	/**
	 * Copies the payload data to a byte array.
	 * 
	 * @param target
	 *            the target byte array
	 * @param targetOffset
	 *            the offset in the target byte array
	 */
	public void copyTo(byte[] target, int targetOffset) {
		if (this.length > target.length + targetOffset) {
			throw new ArrayIndexOutOfBoundsException();
		}
		System.arraycopy(this.data, this.offset, target, targetOffset,
				this.length);
	}

	/**
	 * Clones this payload by creating a copy of the underlying byte array.
	 */
	public Object clone() {
		Payload clone = new Payload(this.toByteArray());
		return clone;
	}
}
